Jee lost her foster father (Pa), and Koo lost his girlfriend (Chi). Pa gave Jee a song that was written by Chi, and now Jee returns Chi's letter to Koo. Jee and Koo seem to meet by chance, but in fact Pa and Chi were working partners. Because of the secret mission of Pa and Chi, they link Jee and Koo together.人與人之間應該怎樣生活下去？Ｊｅｅ（潔）失去養父Ｐａ（柏），Ｋｏｏ（顧）失去愛人旨孑；柏將旨孑的樂曲送給了潔，而潔又將旨孑的信交到顧手中，潔和顧的相遇好像是偶然的，其實冥冥之中自有主宰。原來柏和旨孑是相識的，兩人擁有神秘身分和任務，把潔和顧這兩位各不相關的人，於茫茫人海中牽引在一起。
